This application claims the priority of German application 100 33 291.9, filed Jul. 7, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a camshaft for the operation of valves of an internal-combustion engine including a device for hydraulic adjustment of a relative rotating position of the camshaft for influencing a timing of the valves. The device has a drive wheel for the camshaft, a cell wheel, and an impeller which, by way of radial vanes, is disposed within cells of the cell wheel and is able to carry out a relative motion. A locking arrangement, operative in a starting phase of the internal-combustion engine, is provided between the cell wheel and the impeller. The locking arrangement is formed by an axially spring-loaded, hydraulically operated piston, which is accommodated in one of the vanes of the impeller, and a corresponding receiving device for the piston, which is provided in a constructional unit consisting of the drive wheel and the cell wheel.
German Patent Document DE 39 37 644 A1 concerns a known camshaft of the type mentioned above. A locking arrangement is provided in this known camshaft. In the starting phase of the internal-combustion engine, the locking arrangement fixes the impeller relative to the cell wheel to avoid uncontrolled movements of the two wheels with respect to one another. Such uncontrolled movements, among other things, can cause disturbing sounds. The locking arrangement comprises a slidably movable locking sleeve arranged coaxially between the cell wheel and the impeller. The locking sleeve non-rotatably connects the above-mentioned wheels with one another in a first position and separates them from one another in a second position.
In German Patent Document DE 1 96 23 818 A1, a corresponding locking device is provided between a vane-type extension of an impeller and a cover of the cell wheel. The locking arrangement is provided with a spring-loaded axially movable piston. In the starting phase of the internal-combustion engine, this piston engages in a receiving device of the cover.
It is an object of this invention to improve a locking arrangement of a device for adjusting the relative rotating position of a camshaft such that it can easily be integrated in the device and functions well.
According to the invention, this object is achieved by providing a piston which has a locking section projecting into the receiving device and guided in one of the vanes of the device. An operating element with which the piston cooperates is provided. The piston is acted upon by a first pressure space, and the operating element is acted upon by a second pressure space. Additional characteristics and further developments of the invention are reflected in the claims.
The principal advantages achieved by the invention are that the piston and the operating element cooperating therewith, which can be acted upon from separate pressure spaces, ensure a reliable and immediate effect of the locking arrangement of the device for adjusting the relative rotating position of the camshaft. The operating element, constructed as a pin, and the piston can be integrated in a simple and spatially favorable manner in the vane of the impeller of the device. Furthermore, the piston and the pin are components which can be produced at acceptable expenditures and mounted easily.
The drawings illustrate an embodiment of the invention which will be described in detail.